Supervisory Control and Data Acquisition (SCADA) systems make use of nonsynchronous data with low density sampling rates to monitor power systems. However, the measurements collected from SCADA do not capture the system dynamics. Phasor measurement units (PMUs) equipped with GPS antennas can be used to provide voltage and current phasors as well as frequency with a high density sampling rate up to 60 Hz. The PMU data can capture the system electromechanical dynamics.